New radiators - totally baffled!

FreeBear

A1ps said: Can I be cheeky please, and ask for recommendations on these rooms too please?

Need to know how many exterior walls, and type (cavity, insulated/uninsulated) and what is above & below.

And in my opinion, in a well insulated draught free house, there is no real need to site radiators under windows. I've moved all mine to internal walls which helped to rationalise the plumbing and keep the pipes relatively short.

Albermarle

@Albermarle would you mind me asking the width and depth of your loft room please?

Our loft room is around 5M X 5M, but two of the sides are sloping, so usable space is about the same as your bedroom.

Your loft room sounds much larger, and will need the two radiators, otherwise will be difficult to get evenly warm.
Is it well insulated ( unlike the bedroom) ?

ThisIsWeird

A1ps said:

I just checked my flow temperature on the boiler - it is in fact 65 degrees NOT 55 as I guessed before.

@ThisIsWeird thanks for the link. I'm going to measure the window width tonight to make sure this size fits the width. If not, will look at ones that do fit. 

Are there any negatives for going for FloMasta over the Stelrad? Price isn't an issue as I want to make sure I get it right first time round, regardless of cost.

A 65oC flow temp makes sense, as a 55o temp runs the risk of not heating your hot water cylinder adequately to guard against Legionnaire's.

Re making the rad suit the window - that was partly said in jest, as the most crude way to determine the 'correct' rad size. It was based on some info, tho', and the assumption that a 1600mm rad, at 2.1kW, should be ok for that room. FreeBear has pointed out, tho', that a reduced flow temp will seriously affect the rad's output, so even 1600mm might not be large enough. And, yes, I was taken aback by the jump in cost. But, if you want to heat a room properly, run it on cooler water, then make sure the rad is 'big enough'.

In short, you cannot fit a rad that's 'too' big.

A thought - try a look on Facebook Marketplace. I've just tried that over here, and there's a good selection of second hand rads, in very good condition, for £5 a pop. There's even an ad for 5 brand new rads for £150 - 2 are 1200mm.

What I'm basically saying is, absolutely do the 'calcs' so's you have a baseline to compare by, but - more than this - judge what the new size should be by the performance of the existing. That 900mm one in your bedroom, for example, by your own account is just ain't cutting the mustard, so you will need an increase based on just how little mustard-cutting it is achieving. If it's 'almost' good enough, then perhaps three or four hundred more watts will be fine? If it's 'well chill', then you'll likely need the best part of an extra kW. And then add some 'over-sizing' if you can, to allow you to turn the boiler flow down. What size do you end up with? Does it seem ok? Worth edging up another size unit? Adding extra fins?!

It's a very rough science - unless you have a modern home, insulated to a high degree. Then you can choose rads with some precision.

A1ps

BarelySentientAI said:

Some people say that Flomasta are lower quality and more prone to springing leaks.

Then again, you will always find some bad reviews of any product.

Absolutely agree. People normally go on to leave reviews when they're unhappy. Very rarely when things are great.

A1ps

FreeBear said:

A1ps said: Can I be cheeky please, and ask for recommendations on these rooms too please?

Need to know how many exterior walls, and type (cavity, insulated/uninsulated) and what is above & below.

And in my opinion, in a well insulated draught free house, there is no real need to site radiators under windows. I've moved all mine to internal walls which helped to rationalise the plumbing and keep the pipes relatively short.

Ahhh, yes. 

Kids room - W 4 x L 3 x H 2.3 Window Area 2.4m2 Radiator would have to be 600 x 900 due to space
2 external walls. Heated room above and below.

Mum's room - W 4 x L 2 x H 2.3 Window Area 2.4m2 Radiator would have to be 600 x 600 due to space
1 external wall. Heated room above and below.

Loft - W 8 x L 5 x H 2.3 Window Area 2 m2
4 external walls. Heated room below. Poor excuse of an insulated roof above.

Hallway - W 6.2 x L 2 x H 2.3 Window Area No windows   Radiator would have to be 600 x 900 due to space
No external walls. Heated room above and below.

Unfortunately, my house (and the one next door) was built by a cowboy, so poor insulation and building work all round. 

A1ps

ThisIsWeird said:

A1ps said:

I just checked my flow temperature on the boiler - it is in fact 65 degrees NOT 55 as I guessed before.

@ThisIsWeird thanks for the link. I'm going to measure the window width tonight to make sure this size fits the width. If not, will look at ones that do fit. 

Are there any negatives for going for FloMasta over the Stelrad? Price isn't an issue as I want to make sure I get it right first time round, regardless of cost.

A 65oC flow temp makes sense, as a 55o temp runs the risk of not heating your hot water cylinder adequately to guard against Legionnaire's.

Re making the rad suit the window - that was partly said in jest, as the most crude way to determine the 'correct' rad size. It was based on some info, tho', and the assumption that a 1600mm rad, at 2.1kW, should be ok for that room. FreeBear has pointed out, tho', that a reduced flow temp will seriously affect the rad's output, so even 1600mm might not be large enough. And, yes, I was taken aback by the jump in cost. But, if you want to heat a room properly, run it on cooler water, then make sure the rad is 'big enough'.

In short, you cannot fit a rad that's 'too' big.

A thought - try a look on Facebook Marketplace. I've just tried that over here, and there's a good selection of second hand rads, in very good condition, for £5 a pop. There's even an ad for 5 brand new rads for £150 - 2 are 1200mm.

What I'm basically saying is, absolutely do the 'calcs' so's you have a baseline to compare by, but - more than this - judge what the new size should be by the performance of the existing. That 900mm one in your bedroom, for example, by your own account is just ain't cutting the mustard, so you will need an increase based on just how little mustard-cutting it is achieving. If it's 'almost' good enough, then perhaps three or four hundred more watts will be fine? If it's 'well chill', then you'll likely need the best part of an extra kW. And then add some 'over-sizing' if you can, to allow you to turn the boiler flow down. What size do you end up with? Does it seem ok? Worth edging up another size unit? Adding extra fins?!

It's a very rough science - unless you have a modern home, insulated to a high degree. Then you can choose rads with some precision.

I feel proper silly right now as I actually went and done the measurements and was going to come back and say just how super big and impractical that size would be... and how silly it would look   I'm laughing as I type this  

The max I could go is 1100 as any more than that would encroach on the area by the bedside cabinet.

Regarding the hot water temp - that is 60 right now and as it stands is scolding hot. I was actually going to lower it to 55, but if that's not a good idea due to risk of Legionnaire's, I'll leave it as it is.

The radiator temp is 65 at 2.7 bar.

A1ps

Albermarle said:

@Albermarle would you mind me asking the width and depth of your loft room please?

Our loft room is around 5M X 5M, but two of the sides are sloping, so usable space is about the same as your bedroom.

Your loft room sounds much larger, and will need the two radiators, otherwise will be difficult to get evenly warm.
Is it well insulated ( unlike the bedroom) ?

Like the rest of the house, very poorly insulated. In winter, the loft, my room and the kids room heat up OK, but as soon as the rads go off, the temperature drops very quickly. 

We changed all the windows, dropped insulation between the window area where the radiators are. Still the heat seeps out. Mum's room though is great. 

ThisIsWeird

A1ps said:

ThisIsWeird said:

A1ps said:

I just checked my flow temperature on the boiler - it is in fact 65 degrees NOT 55 as I guessed before.

@ThisIsWeird thanks for the link. I'm going to measure the window width tonight to make sure this size fits the width. If not, will look at ones that do fit. 

Are there any negatives for going for FloMasta over the Stelrad? Price isn't an issue as I want to make sure I get it right first time round, regardless of cost.

A 65oC flow temp makes sense, as a 55o temp runs the risk of not heating your hot water cylinder adequately to guard against Legionnaire's.

Re making the rad suit the window - that was partly said in jest, as the most crude way to determine the 'correct' rad size. It was based on some info, tho', and the assumption that a 1600mm rad, at 2.1kW, should be ok for that room. FreeBear has pointed out, tho', that a reduced flow temp will seriously affect the rad's output, so even 1600mm might not be large enough. And, yes, I was taken aback by the jump in cost. But, if you want to heat a room properly, run it on cooler water, then make sure the rad is 'big enough'.

In short, you cannot fit a rad that's 'too' big.

A thought - try a look on Facebook Marketplace. I've just tried that over here, and there's a good selection of second hand rads, in very good condition, for £5 a pop. There's even an ad for 5 brand new rads for £150 - 2 are 1200mm.

What I'm basically saying is, absolutely do the 'calcs' so's you have a baseline to compare by, but - more than this - judge what the new size should be by the performance of the existing. That 900mm one in your bedroom, for example, by your own account is just ain't cutting the mustard, so you will need an increase based on just how little mustard-cutting it is achieving. If it's 'almost' good enough, then perhaps three or four hundred more watts will be fine? If it's 'well chill', then you'll likely need the best part of an extra kW. And then add some 'over-sizing' if you can, to allow you to turn the boiler flow down. What size do you end up with? Does it seem ok? Worth edging up another size unit? Adding extra fins?!

It's a very rough science - unless you have a modern home, insulated to a high degree. Then you can choose rads with some precision.

I feel proper silly right now as I actually went and done the measurements and was going to come back and say just how super big and impractical that size would be... and how silly it would look   I'm laughing as I type this  

The max I could go is 1100 as any more than that would encroach on the area by the bedside cabinet.

Regarding the hot water temp - that is 60 right now and as it stands is scolding hot. I was actually going to lower it to 55, but if that's not a good idea due to risk of Legionnaire's, I'll leave it as it is.

The radiator temp is 65 at 2.7 bar.

I was only half joking, even less.
A 1100mm rad ain't much more powerful than what you currently have, and certainly won't be effective if you do turn down the boiler flow temp.
I'd personally still oversize.
60o for your DHW is perfectly fine. You'd prob get away with it less, as Leg would struggle to survive in that, but - again personally - I'd leave it at 60, or close to.
Your boiler pressure is 2.7bar? That has no bearing on the temp, but is actually uncomfortably high for the system - it'll activate a safety valve at 3bar.
What pressure is it at when cold?

FreeBear

A1ps said: Regarding the hot water temp - that is 60 right now and as it stands is scolding hot. I was actually going to lower it to 55, but if that's not a good idea due to risk of Legionnaire's, I'll leave it as it is.

If you have a combi boiler or an unvented hot water tank, you will be perfectly safe dropping the water temperature down to 50°C. Even with a vented system with a header tank up in the loft, the risk of legionella is extremely low - You have a better chance of being hit by a No.13 bus.

Yes, if you have an open header tank where birds can poop in the water, there is an increased risk, but how many domestic properties have such a thing.

Albermarle

FreeBear said:

A1ps said: Regarding the hot water temp - that is 60 right now and as it stands is scolding hot. I was actually going to lower it to 55, but if that's not a good idea due to risk of Legionnaire's, I'll leave it as it is.

If you have a combi boiler or an unvented hot water tank, you will be perfectly safe dropping the water temperature down to 50°C. Even with a vented system with a header tank up in the loft, the risk of legionella is extremely low - You have a better chance of being hit by a No.13 bus.

Yes, if you have an open header tank where birds can poop in the water, there is an increased risk, but how many domestic properties have such a thing.

Plus if it is a family home with a regular/daily usage of hot water, the very minimal risk becomes even more minute.